MCP DuckDB Geospatial Data Server

Documentation

A Model Context Protocol (MCP) server that provides SQL query access to large-scale geospatial datasets stored in S3. Built with DuckDB for high-performance analytics on H3-indexed environmental, biodiversity, and geospatial data.

Quick Start

Add the hosted MCP endpoint to your LLM client, like so:

Using VSCode

create a .vscode/mcp.json like this: (as in this repo)

{
	"servers": {
		"duckdb-geo": {
			"url": "https://duckdb-mcp.nrp-nautilus.io/mcp"
		}
	}
}

Now simply ask your chat client a question about the datasets and it should answer by querying the database in SQL:

Examples:

• What fraction of Australia is protected area?

Using Claude Code (Desktop)

Add to your Claude Desktop configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json
Linux: ~/.config/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "duckdb-geo": {
      "url": "https://duckdb-mcp.nrp-nautilus.io/mcp"
    }
  }
}

After adding the configuration, restart Claude Desktop.

Features

• Zero-Configuration SQL Access: Query petabytes of geospatial data without database setup
• H3 Geospatial Indexing: Efficient spatial operations using Uber's H3 hexagonal grid system
• Isolated Execution: Each query runs in a fresh DuckDB instance for security
• Stateless HTTP Mode: Fully horizontally scalable for cloud deployment
• Rich Dataset Catalog: Access to 10+ curated environmental and biodiversity datasets
• MCP Resources & Prompts: Browse datasets and get query guidance through MCP protocol

Available Datasets

The example configuration provides access to the following datasets via S3:

1. GLWD - Global Lakes and Wetlands Database
2. Vulnerable Carbon - Conservation International carbon vulnerability data
3. NCP - Nature Contributions to People biodiversity scores
4. Countries & Regions - Global administrative boundaries (Overture Maps)
5. WDPA - World Database on Protected Areas
6. Ramsar Sites - Wetlands of International Importance
7. HydroBASINS - Global watershed boundaries (levels 3-6)
8. iNaturalist - Species occurrence range maps
9. Corruption Index 2024 - Transparency International data

Datasets are discovered dynamically from the STAC catalog via the list_datasets and get_dataset tools.

Local Development

You can also run the server locally

Or install dependencies and run directly:

pip install -r requirements.txt
python server.py

You can now connect to the server over localhost (note http not https here), e.g. in VSCode:

{
	"servers": {
			"duckdb-geo": {
			"url": "http://localhost:8000/mcp"
		},
	}
}

You can adjust the instructions to the LLM in the corresponding .md files (e.g. query-optimization.md, h3-guide.md). You will need to adjust query-setup.md to run the server locally, as it uses endpoint and thread count that only work from inside our k8s cluster. Running locally means your local CPU+network resources will be used for the computation, which will likely be much slower than the hosted k8s endpoint.

Architecture

We have a fully-hosted version

Core Components

• server.py - Main MCP server with FastMCP framework
• stac.py - STAC catalog integration for dynamic dataset discovery

Runtime Prompt Files

The .md files in this repo are not documentation — they are curated prompt content loaded by server.py at startup and injected directly into MCP tool descriptions and prompts at runtime. The agent (LLM) reads them as instructions, not humans.

File	How it is used
query-setup.md	SQL parsed and executed in every fresh DuckDB connection before a query runs
query-optimization.md	Injected verbatim into the query tool description
h3-guide.md	Injected verbatim into the query tool description
assistant-role.md	Served as the geospatial-analyst MCP prompt (role + response style)

Editing these files changes what the agent is told to do. They must be written for a stateless LLM — short, concrete, and unambiguous. See AGENTS.md for editing rules.

Key Design Patterns

1. Isolation Engine: Each query runs in a fresh duckdb.connect(":memory:") — no state or credentials survive between requests
2. Context Injection: Prompt files are embedded into tool descriptions so even MCP clients that don't support prompts/list receive the guidance
3. Partition Pruning: H3 resolution columns (h0) enable DuckDB to skip S3 partitions, giving 5–20× speedups on large datasets

Kubernetes Deployment

Deploy to Kubernetes using the provided manifests:

kubectl apply -f k8s/deployment.yaml
kubectl apply -f k8s/service.yaml
kubectl apply -f k8s/ingress.yaml

The deployment:

• Runs 2 replicas for high availability
• Allocates 16GB memory per pod for large queries
• Uses uv for fast dependency installation
• Includes readiness probes for safe rollouts

MCP Protocol Features

Tools

• browse_stac_catalog(catalog_url?, catalog_token?) - List available datasets from the STAC catalog
• get_stac_details(dataset_id, catalog_url?, catalog_token?) - Get S3 paths and schema for a dataset
• query(sql_query, s3_key?, s3_secret?, s3_endpoint?, s3_scope?) - Execute DuckDB SQL against S3 parquet files

Resources

NOTE: Some MCP clients, like in VSCode, do not recognize "resources" and "prompts". Newer clients (Claude code, Continue.dev, Antigravity do)

• catalog://list - List all available datasets
• catalog://{name} - Get detailed schema for a specific dataset

Prompts

• geospatial-analyst - Load complete context for geospatial analysis persona

Query Optimization Tips

1. Always include h0 in joins - Enables partition pruning for 5-20x speedup
2. Use APPROX_COUNT_DISTINCT(h8) - Fast area calculations with H3 hexagons
3. Filter small tables first - Create CTEs to reduce join cardinality
4. Set THREADS=100 - Parallel S3 reads are I/O bound, not CPU bound
5. Enable object cache - Reduces redundant S3 requests

See query-optimization.md for detailed guidance.

H3 Spatial Operations

All datasets use Uber's H3 hexagonal grid system for spatial indexing:

• Resolution 8 (h8): ~0.737 km² per hex
• Resolution 0-4 (h0-h4): Coarser resolutions for global analysis
• Use h3_cell_to_parent() to join datasets at different resolutions
• Use APPROX_COUNT_DISTINCT(h8) * 0.737327598 to calculate areas in km²

Testing

# Run all tests
pytest tests/

# Run specific test file
pytest tests/test_server.py

# Run with coverage
pytest --cov=. tests/

Configuration

Environment Variables

• THREADS - DuckDB thread count (default: 100 for S3 workloads)
• PORT - HTTP server port (default: 8000)

DuckDB Settings

Required settings are documented in query-setup.md and automatically injected into query tool descriptions.

Private Data Access

The server supports private STAC catalogs and private S3 buckets. Credentials are supplied per-call by the client and are scoped to that request only — they are never logged, cached, or shared between clients.

Private STAC catalog

If your STAC catalog requires authentication, pass a bearer token alongside the catalog URL:

{ "tool": "list_datasets", "arguments": {
    "catalog_url": "https://your-app.example.org/stac/catalog.json",
    "catalog_token": "YOUR_BEARER_TOKEN"
}}

The token is forwarded as Authorization: Bearer <token> when fetching catalog JSON. Pass the same catalog_url and catalog_token to get_dataset as well.

Serving a private catalog: The catalog endpoint needs to accept bearer token authentication for machine-to-machine access. If you are using oauth2-proxy for human (browser) access, add a parallel nginx auth_request bypass for the /stac/ path that accepts a static shared token via the Authorization header. This allows the MCP server to fetch catalog metadata without requiring a browser OAuth session.

Private S3 data

Pass S3 credentials directly to the query tool. The server injects them as a scoped DuckDB secret for the duration of that query, then destroys the connection:

{ "tool": "query", "arguments": {
    "sql_query": "SELECT * FROM read_parquet('s3://my-private-bucket/data/**') LIMIT 10",
    "s3_key": "YOUR_ACCESS_KEY_ID",
    "s3_secret": "YOUR_SECRET_ACCESS_KEY",
    "s3_endpoint": "minio.example.org"
}}

s3_endpoint defaults to s3-west.nrp-nautilus.io if omitted. SSL is enabled automatically for non-Ceph endpoints.

Security properties

Concern	How it is handled
Credential bleed between clients	Each request uses a separate duckdb.connect(":memory:") — DuckDB secrets are connection-scoped and destroyed on close
Credentials in server logs	CREATE SECRET statements are constructed internally and never written to stderr
Credentials in transit	All traffic is TLS-terminated at the ingress
Credential persistence	stateless_http=True — no session state survives between requests

Deploying private apps without a separate server

Rather than maintaining a forked server deployment per app, private geo-agent apps can share the public MCP server endpoint and pass their credentials per-call. This reduces idle deployments and ensures all apps benefit from server improvements automatically.

Security

• Stateless Design: No persistent database or user data
• Query Isolation: Each request gets a fresh DuckDB instance; client credentials cannot bleed across requests
• DNS Rebinding Protection: Disabled for MCP HTTP mode

License

MIT License - See repository for details

Contributing

Contributions welcome! Key areas:

• Additional dataset integrations
• Query optimization patterns
• STAC catalog enhancements
• Documentation improvements

References

• Model Context Protocol
• DuckDB Documentation
• H3 Geospatial Indexing
• FastMCP Framework
• STAC Specification

Support

For issues and questions:

• GitHub Issues: boettiger-lab/mcp-data-server
• Dataset questions: Use the browse_stac_catalog tool or browse the public STAC catalog